Method, system, device and medium for determining a blood flow velocity in a vessel

Abstract

Method, system, device and medium for determining a blood flow velocity in a vessel are provided. An example method includes receiving a 3D model of the vessel, which is reconstructed based on X-ray angiography images of the vessel. The method further includes specifying a segment of the 3D model by a start landmark and a termination landmark. Moreover, the method includes determining the blood flow velocity based on length of the segment and perfusion time for the segment by normalizing the blood flow velocity to correspond to a cardiac cycle. The method has a better accuracy in calculating blood flow velocity, and requires no additional modalities other than the original X-ray angiogram sequences used to visualize coronary arteries.

The invention claimed is: 
     
       1. A method for determining a blood flow velocity in a vessel, comprising:
 receiving, at an interface of a device, a 3D model of the vessel, the 3D model reconstructed based on X-ray angiography images of the vessel; 
 specifying, by a processor of the device, a segment of the 3D model by a start landmark and a termination landmark; and 
 determining, by the processor, the blood flow velocity based on length of the segment and perfusion time for the segment by normalizing the blood flow velocity to correspond to a cardiac cycle, 
 wherein a device for medical intervention is controlled based on the determined blood flow velocity. 
 
     
     
       2. The method of  claim 1 , wherein when the perfusion time is longer than the cardiac cycle, normalizing the blood flow velocity to correspond to a cardiac cycle comprises:
 relocating the termination landmark where blood perfuses to a new frame one cardiac cycle after a first frame where the blood perfuses the start landmark. 
 
     
     
       3. The method of  claim 1 , wherein when the perfusion time is shorter than the cardiac cycle, normalizing the blood flow velocity to correspond to a cardiac cycle comprises:
 determining a first frame where blood perfuses the start landmark and a second frame where blood perfuses the termination landmark; 
 mapping the phases of the first frame and the second frame to a theoretical instantaneous blood flow profile; 
 determining the ratio of the blood flow velocity corresponding to the period between the mapped phases and the blood flow velocity corresponding to the cardiac cycle based on the theoretical instantaneous blood flow profile; and 
 dividing the determined blood flow velocity for the segment by the ratio to obtain the normalized blood flow velocity. 
 
     
     
       4. The method of  claim 1 , wherein the vessel comprises a coronary artery. 
     
     
       5. The method of  claim 1 , further comprising calculating the perfusion time by:
 determining a first frame where blood perfuses the start landmark and a second frame where blood perfuses the termination landmark; 
 determining a frame number difference between the first and second frames; and 
 dividing the frame number difference by a frame rate to obtain the perfusion time. 
 
     
     
       6. The method of  claim 1 , further comprising:
 estimating the cardiac cycle automatically. 
 
     
     
       7. The method of  claim 6 , wherein estimating the cardiac cycle automatically comprises:
 tracking a motion of a track landmark remaining immobile relative to an aorta; 
 identifying the systole end points from the motion of the track landmark; and 
 averaging the intervals between each pair of adjacent systole end points to obtain the cardiac cycle. 
 
     
     
       8. The method of  claim 7 , wherein the track landmark is located at a tip of a catheter for coronary angiography. 
     
     
       9. A system for determining a blood flow velocity in a vessel, comprising:
 an interface configured to receive a 3D model of the vessel, the 3D model reconstructed based on X-ray angiography images of the vessel; 
 a processor configured to: 
 specify a segment of the 3D model by a start landmark and a termination landmark; and 
 determine the blood flow velocity based on length of the segment and perfusion time for the segment by normalizing the blood flow velocity to correspond to a cardiac cycle, 
 wherein a device for medical intervention is controlled based on the determined blood flow velocity. 
 
     
     
       10. The system of  claim 9 , wherein when the perfusion time is longer than the cardiac cycle, the processor is further configured to, when normalizing the blood flow velocity to correspond to a cardiac cycle:
 relocate the termination landmark where blood perfuses to a new frame one cardiac cycle after a first frame where the blood perfuses the start landmark. 
 
     
     
       11. The system of  claim 9 , wherein when the perfusion time is less than the cardiac cycle, the processor is further configured to, when normalizing the blood flow velocity to correspond to a cardiac cycle:
 determine a first frame where blood perfuses the start landmark and a second frame where blood perfuses the termination landmark; 
 map the phases of the first frame and the second frame to a theoretical instantaneous blood flow profile; 
 determine the ratio of the blood flow velocity corresponding to the period between the mapped phases and the blood flow velocity corresponding to the cardiac cycle based on the theoretical instantaneous blood flow profile; and 
 divide the determined blood flow velocity for the segment by the ratio to obtain the normalized blood flow velocity. 
 
     
     
       12. The system of  claim 9 , wherein the processor is further configured to estimate the cardiac cycle automatically. 
     
     
       13. The system of  claim 12 , wherein the processor is configured to, when estimating the cardiac cycle automatically:
 track a motion of a track landmark remaining immobile relative to an aorta; 
 identify the systole end points from the motion of the track landmark; and 
 average the intervals between each pair of adjacent systole end points to obtain the cardiac cycle. 
 
     
     
       14. The system of  claim 13 , wherein the track landmark is located at a tip of a catheter for coronary angiography. 
     
     
       15. A non-transitory computer readable medium storing instructions that, when executed by a processor, perform a method, the method comprising:
 receiving a 3D model of the vessel, the 3D model reconstructed based on X-ray angiography images of the vessel; 
 specifying, by a processor, a segment of the 3D model by a start landmark and a termination landmark; and 
 determining, by the processor, the blood flow velocity based on length of the segment and perfusion time for the segment by normalizing the blood flow velocity to correspond to a cardiac cycle, 
 wherein a device for medical intervention is controlled based on the determined blood flow velocity. 
 
     
     
       16. The non-transitory computer readable medium of  claim 15 , wherein when the perfusion time is longer than the cardiac cycle, normalizing the blood flow velocity to correspond to a cardiac cycle comprises:
 relocating the termination landmark where blood perfuses to a new frame one cardiac cycle after a first frame where the blood perfuses the start landmark. 
 
     
     
       17. The non-transitory computer readable medium of  claim 15 , wherein when the perfusion time is less than the cardiac cycle, normalizing the blood flow velocity to correspond to a cardiac cycle comprises:
 determining a first frame where blood perfuses the start landmark and a second frame where blood perfuses the termination landmark; 
 mapping the phases of the first frame and the second frame to a theoretical instantaneous blood flow profile; 
 determining the ratio of the blood flow velocity corresponding to the period between the mapped phases and the blood flow velocity corresponding to the cardiac cycle based on the theoretical instantaneous blood flow profile; and 
 dividing the determined blood flow velocity for the segment by the ratio to obtain the normalized blood flow velocity. 
 
     
     
       18. The non-transitory computer readable medium of  claim 15 , the method further comprising calculating the perfusion time by:
 determining a first frame where blood perfuses the start landmark and a second frame where blood perfuses the termination landmark; 
 determining a frame number difference between the first and second frames; and 
 dividing the frame number difference by a frame rate to obtain the perfusion time. 
 
     
     
       19. The non-transitory computer readable medium of  claim 15 , the method further comprising:
 estimating the cardiac cycle automatically. 
 
     
     
       20. The non-transitory computer readable medium of  claim 19 , wherein estimating the cardiac cycle automatically comprises:
 tracking a motion of a track landmark remaining immobile relative to an aorta; 
 identifying the systole end points from the motion of the track landmark; and 
 averaging the intervals between each pair of adjacent systole end points to obtain the cardiac cycle.